Silk screen print dryer



A. MAESCHER 2,907,118

SILK SCREEN PRINT DRYER Oct. 6, 1959 Filed April 6, 1956 2 Sheets-Sheet 1 Oct. 6, 1959 A. MAESCHER SILK SCREEN PRINT DRYER 2 Sheets-Sheet 2 Filed April 6, 1956 United States Patent SILK SCREEN PRINT DRYER Albert Maescher, St. Louis, Mo., assignor, by mesne assignments, to Cardel Electric Co. Inc., Cincinnati, Ohio, a corporation of Indiana The present invention relates to the silk screen printing field and specifically contemplates a dryer for materials printed by the silk screen processes.

vIn connection with the preparation of large posters and advertising display, particularly where multicolor media is desired, the silk screen process is employed for reproducing prints on a wide variety of materials. In the process a fine grade of silk is stretched across a frame, and treated with a gelatinous substance so that only the untreated area will pass the printing ink into material to be printed. After the sheets have been printed, it is necessary that they be dried before additional colors can be applied and also before they can be stacked for storage and eventual shipment.

Many expedients have been resorted to for drying. One well known device is the wicket dryer in which the printed material is stacked in plurality of Wire wickets which travel along a longitudinal axis holding the sheets until they air dry. In other instances, the sheets may be merely stacked in horizontal slots in a fixed jig.

In the shop where there are short runs of a wide variety of material, varying in size, as well as the pattern being printed, there has been a long-felt need for a high speed dryer which is also inexpensive to build and operate. A dryer which works with an air blower would be more desirable, particularly where the air has been heated and passes over the printed material as it travels through the dryer on an endless belt. Such a dryer was disclosed in the Silk Screen Process magazine, October 1954 issue at page 36, et seq. As indicated in the article, however, the dryer is quite noisy in operation. In addition, a distinct problem is introduced when air jets are employed improperly holding the printed material on the belt as it passes through the dryer so that it does not blow around and mar the printed surface.

With the foregoing in mind it is the general object of the present invention to provide a silk screen processed material dryer which efficiently and rapidly dries silk screen printed material with a hot air blast.

Another object of the present invention is to furnish a hot air silk screen print dryer which is quiet in operation and yet is effective to dry the printed material in a single pass through the dryer.

Still another object of the invention is to furnish a silk screen dryer which incorporates pneumatic work pieces engaging features thereby ensuring proper register of the material as it passes through the dryer.

A further object of the invention is to provide a silk screen dryer with a variably adjustable pneumatic working engaging element permitting the accommodation of conjunction with the accompanying drawings in which:

Figure 1 is a perspective view of a typical screen dryer incorporating the features of, the present invention.

Z,97,ll8 Patented Oct. 6,1959

Fig. 2 is a top view of the dryer shown in Fig. 1.

Fig. 3 is a front elevation of the dryer shown in Fig. 2 in the same scale as shown in Fig. 2.

Fig. 4 is an end view of the dryer shown in Figs. 2 and 3 on the same scale as shown in Figs. 2 and 3.

Fig. 5 is a bottom broken View of the adjustable work engagingjet mechanism.

Fig. 6 is a transverse cross-sectional View of the blower mechanism taken along section line 6-6 of Fig. 2.

Fig. 7 is a top view in an enlarged scale showing a corner of the jet plate inside dryer unit.

Fig. 8 is a sectional view taken along section 88 of Fig. 7 showing the arrangement of the holes in the jet plate illustrated in Fig. 7.

Fig. 9 is a broken end view of the jet plate shown in Fig. 7 illustrating its assembled relationship for use in the dryer.

In broad outline, the dryer 10 to be described serves to illustrate an exemplary embodiment of the invention. The dryer contemplates a long fiat moving endless belt assembly 11 (as best illustrated in Figs. 1 and 2) which is actually made up of a plurality of belts 12. A closed path' hot air circulating system 14 surrounds the midportion of the moving belt assembly '11. Within the closed path hot air system the unique perforated plate 15 is placed to cause the air to impinge upon the work piece as a plurality of small jets. The exhaust system co-acts with the various jets to firmly engage and hold the work on the belt by a dynamic air movement thereby ensuring the proper positioning and travel of the work pieces through the dryer. An auxiliary adjustable jet system assembly 16 may be employed to further implement work engagement and proper feed through the dryer.

In more specific detail, it will be seen that the dryer has a frame assembly 20 which includes a plurality of legs 21 which are joined tothe frame side members 22 and members 24. The frame side members 22 serve as supports for the pillow block bearing assemblies 25 which in turn journal the belt rollers 26. Intermediate belt supports 28 may be employed where the belt span would induce an objectionable amount of slack in the belts '12. The belt support assembly 28 is in the form of a transverse member with a supporting flange 29. In the present instance the belt supporting assembly 28 has been employed at the discharge portion of the unit where the endless belt table portion is longer than at the entrance to the unit.

As will be seen, the belts are separated at the terminal rollers .at a distance in excess of the width of a belt. Between the two middle rollers this provides a more continuoussupport area as the Work piece passes through the hot air circulating system 14. The belting system is driven by an electric motor 30 through a belt and gear train assembly 31 to drive the roller 26 which is immedie ately adjacent the entrance to the closed hot air drying system 14. I

As will be seen particularly by reference to Fig. 6, the path of air in the hot air circulating system 14 moves in a modified circular path. The air is driven by a centrifugal blower assembly 34, the power to which is sup-,

plied by an electric motor 35 by a belt drive 36. The blower assembly 34 is located beneath the moving belt but within a closed portion of the path of circulating air. The air is driven upwardly from the blower assembly 34 through the heating duct 38 and into the heater assembly 39. The heater assembly 39 contemplates a plurality of heat exchange elements 40 which may be in the form of staggered chrome-nichrome electrically heated elements. Although such a device has been found most satisfactory in a commercial embodiment of the invention, other units which would raise. thetemperature of the air-and yet permit its ready passage'through the heater duct 38 would be satisfactory.

After the air has been heated it is then directed by the hood 41 over toward the work. The hood 41 is completely traversed in'its inner portion by the jet plate: 15. It is inthe specific construction ofthe jet plate 15' that many of the unique features of the invention are found, and" particularly in'tbe cooperative relationship between the jet'plate and thejexhaust ducting. The jet plate. 1'5, may be readily prepared from a one-fourth inch material, the pressed wood material sold under the trade name of Masonite having been foundhighly satisfactory for this use.

A plurality of counter-sunk jet holes 44 are drilled in the jet plate. As will be seen' from Fig. 8 the. jet holes themselves are approximately half the diameter of the thickness of" jet plate 15', thus when a one-fourth inch Masonite jet plate 15 is employed the jet hole 45 is oneeighth inch in diameter. The jet'holes are countersunk with an included angle of 60 degrees to a depth approximately half the thickness of the jet plate 15.

At the leading edge of the jet plate 15, two rows. of staggered air curtain ports 46 have been provided; The ports 46 have a diameter equal to the thickness of the jet plate 15. The detailed function and arrangement of the jets 44 and air curtain ports 46 will be described hereinafter, but'will be better understood when the combined operation of the exhaust system and jets is first explained. Referring again to Figs. 2 and 3, it will be seen that a pair of flanking exhaust ducts 50 are provided to feed the blower assembly 34 with air after the warm air has passed over the work piece. The exhaust ducts 50 are connected at their lower ends by a floor 50" to prevent escape of. air from beneath the conveyor and with an extension shroud 51 effectively suck the air off of the work piece and belt assembly after the material has been first cont'acted by the air.

Because the exhaust ducts 50 operate adjacent the entrance and' exit of the material through the hot air circulating system 1 they serve to cooperate with the jet plate in forcing the stream of air to pass over the entire area of the work piece. This action assists in rapidly and thoroughly drying the inked face of the work piece.

Because the air moves in diverse directions upon contacting the work piece, particularly near the entrance to the hot air circulating system 14, a turbulence is set up at the entrance 13. The ports 46 have been provided at the leading edge of the jet plate 15 for the purpose of setting up a curtain of air to confine the turbulence at the entrance 13 to the oven area. This minimizes the tendency of the printed sheets to drift upon approaching the entrance 13. The curtain of air also acts to firmly hold the work piece on the belts 12 as well.

To augment the action of the air curtain provided by the ports 46 an external auxiliary jet system assembly 16 may be provided at the inlet portion of the hot air circulating system 14. The external jet assembly 16, as will be seen in Fig. 5, contemplates an elongated tubular member 52 capped at its ends with caps 54 and secured and fed by support 55. The support 55 is flanked by guide rings 56: secured to the tube 52 which serve to prevent lateral displacement of the tube 52. A convenient port (not shown) is provided in the tube 52 so that the tube may be fed through the support 55 which is in turn coupled to the inside of the hood 41 of the hot air circulating system 14. A plurality of jet holes 58 are provided along a longitudinal axis on the base of the tube shop. By rotating the tube 52 until the connecting port tothe support 55 is shut' ofi; theauxiliarywork engaging assembly 16 may be disengaged. In operation, therefor, two curtains of air are available for cooperation with the flanking exhaust duct 50 to firmly engage the work piece before it enters the turbulent area beneath the jets 44 of the jet plate 15.

Jet: orientation Both the. shape and proportion of. the jets on the jet plate 15 play aroleiir the quiet and etficient operation of the dryer. The jet plate 15 is secured to a jet plate frame 60. The frame 60 is made of angle iron end members 61 and side members 62' which are secured to the hood 41.

As stated above, the jet holes 44 are countersunk to half their depth with a 60 included angle. In practice this countersinking serves the twofold purpose of increasing the effective jet of-ai'r. The-jet'holes'are arranged on center lines which intersect at a 45 anglewith the side and end members 61,.62 of thejetplateframe 603 Although the jetspacingmay be varied, it has been found that when theone eighth inch countersunk holes 45 are used a. spacing; along one inchcenters along the axis parallel-t0 the belt travel is satisfactory;

The jet holes 45 permeate the jetplate 15 and are brought close-to the edges of the frame 60. In practice ithas been found that the jet holes 45 may be brought within one half" inch of the-end frame 61 at the trailing edge 27 and three quarters of an inch from the side frames 62;

A two inchspacing is provided, however, at the leading edge 23 of the jet plate 15 to accommodate the air curtain ports 46. These ports are on three quarter inch longitudinally staggered centers and two inch lateral centers and located within one half inch of the leading cross member 61 of the jet plate'frame- 60. It has also been found desirable to chamfer the ports 46 to a depth of one fourth of the jet plate 15 thickness at an included angle of 60. The jet plate 15 is located about oneinch above the belts 12.

Operation In operationv the air is heated to about 200 F. and the belt speed regulated to pass a thirty inch workpiece into the unit in five to twenty seconds. The air circulates with a static pressure of three and one quarter inches. An electric heater, a blower motor, and a belt motor are the main sources of energy. With such capacities normal silk screen processed sheets can be dried with a, single pass through the dryer.

For cleaning and servicing a side inspection door 43 and removable hood panel 47 have been provided. Thermostatic controls for the heater 39 are provided (not shown) to maintain a preselected operating temperature. Similarly motor speed controls (not shown) are provided to control the static pressure induced by the blower and the speed of belt travel.

Although a particular embodiment of the invention has been shown and described in full here, there is no intention to thereby limit the invention to the details of such embodiment. On the contrary, the intention is to cover allmodifications, alternative embodiments, usages and equivalents of the dryer and running gear as fall within the spirit and scope of the invention, specification and appended claims.

I claim as my invention:

1. A dryer for printed sheets comprising, in combination, a moving conveyor, a housing surrounding the conveyor at a transverse portion thereof, a blower within the housing, the housing. defining an endless air path for air delivered to and discharged from the blower, a heater within the housing to warm the circulating air to a predetermined temperature, a jet plate within the housing and traversingfthe entirety of the air path defined by said housingthe. plate beingcharacterized by leading and.

trailing edges and a plurality of countersunk jet holes therebetween, the plate being oriented above the conveyor, and a pair of exhaust ducts beneath the jet plate leading and trailing edges.

2. A dryer for printed sheets comprising, in combina tion, a moving conveyor, a housing surrounding the conveyor at a transverse portion thereof, a blower within the housing, the housing defining an endless air path for air delivered to and discharged from the blower, a heater within the housing to warm the air to a predetermined temperature, a jet plate within the housing and traversing the entirety of the air path defined by said housing, the plate being characterized by leading and trailing edges and a plurality of jet holes therebetween, the plate being oriented above the conveyor, the jet holes being countersunk at their upstream portion, and a pair of exhaust ducts beneath the jet plate leading and trailing edges to augment the fiow of air at those stations thereby assisting in preventing stray air currents from blowing out of the housing to disturb the insertion of the work piece.

3. A dryer for printed sheets comprising, in combination, a moving conveyor, a housing surrounding the conveyor at a transverse portion thereof, a blower within the housing, the housing defining an endless air path for air delivered to and discharged from the blower, a heater within the housing to warm the circulating air to a predetermined temperature, a jet plate Within the housing and traversing the entirety of the air path defined by said housing; the plate being characterized by leading and trailing edges, a plurality of countersunk jet holes, a plurality of ports staggered along the leading edge of the plate, the plate being oriented above the conveyor; and a pair of exhaust ducts beneath the jet plate leading and trailing edges to augment the fiow of air at those stations thereby assisting in inserting the paper into the dryer.

4. A dryer for printed sheets comprising, in combination, a longitudinal belt, a housing defining an air path having an air blower and heater, said belt passing through said housing a jet plate positioned within the housing and across the air path defined by said housing, exhaust ducts positioned beneath the leading and trailing edges of the jet plate, a plurality of holes in the jet plate on uniformly spaced centers, and a transverse line of holes along the leading edge of the jet plate to provide a curtain of air to initially hold the Work, said work holding holes being at least twice the diameter of the jet holes.

5. A dryer for printed sheets comprising, in combination, a longitudinal belt, a housing defining an endless air path and containing an air blower and heater, a jet plate positioned within the housing and across the air path defined by said housing, said belt passing through said housing, an exhaust duct positioned beneath the jet plate, a plurality of countersunk jet holes in the jet plate on uniformly spaced centers, the countersunk portion of the jet holes being oriented at the upstream portion of the jet plate, and a transverse line of ports along the leading edge of the jet plate, to provide a curtain of air for initially engaging the work.

6. A dryer for printed sheetscomprisiug, in combination, a longitudinal belt, a housing defining an endless air path containing an air blower and heater, said belt passing through said housing, a jet plate positioned within the air path and across the air path defined by said housing, an exhaust duct positioned beneath the jet plate, a plurality of countersunk jet holes in the jet plate on uniformly spaced centers, the jet holes being of a diameter equal to one half the thickness of the jet plate and countersunk to half their depth on the upstream side, and a transverse line of holes for initially engaging the work along the leading edge of the jet plate, the said holes being at least twice the diameter of the jet holes.

7. In a dryer for printed sheets having a longitudinal moving belt and a housing defining an endless path surrounding the mid-portion of the moving belt said belt moving through said housing, said housing having an air heater and blower, the improvement comprising, a jet plate positioned within the housing in parallel relation to the moving belt, the jet plate being characterized by a plurality of jet holes equal in diameter to half the thickness of the plate, the holes being countersunk to half their depth on the upstream side of the air path defined by said housing, and a plurality of transversely spaced holes disposed along the leading edge of the jet plate, the holes along the leading edge of the jet plate being of at least a diameter equal to the thickness of the jet plate to provide a downwardly flowing curtain of air to initially engage the printed sheets fed into the dryer by the moving belt and hold the sheet in axial alinement on the belt until the sheet is well within the dryer.

8. In a dryer for printed sheets having a longitudinal moving belt and housing defining an endless path of circulating air surrounding the mid-portion of the moving belt said belt moving through said housing, the said housing having an air heater and blower, the improvement comprising, a jet plate positioned within the air path in parallel relation to the moving belt, the jet plate being characterized by a plurality of jet holes, the holes being countersunk on the upstream side of the air path defined by said housing, and a pneumatic work engaging element comprising a tube oriented transversely over the belt where the belt enters the housing and having a plurality of exhaust holes, the tube being connected to the closed circuit to deliver air to the exhaust holes which engages the work piece and holds it on the belt.

References Cited in the file of this patent UNITED STATES PATENTS 1,018,992 Spenle Feb. 27, 1912 1,068,845 Benefield July 29, 1913 1,144,896 Fosbreay June 29, 1915 1,980,558 Tandel Nov. 13, 1934 2,196,611 Schneider Apr. 9, 1940 FOREIGN PATENTS 570,774 Great Britain July 23, 1945 

